I concede the terms DLC and Expansion are sometimes used interchangeably. An Expansion is a whole add on or sector etc, a DLC is minor plot lines. Th issue I have is in modern gaming they make DLC which major plot lines, which is NOT fair to those purchasing a game. An Expansion on the other hand is one major upgrade that is not quite a new game in itself.
So a DLC has "minor plot lines", but a DLC can, at the same time, have "major plot lines"?
This is my problem with people trying to make a distinction between expansion and DLC, is that the line being drawn is entirely man-made and makes no logical sense.
"Expansions have story, DLCs don't". Okay, then Citadel, Dragonborn, Dawnguard, Lair of the Shadow Broker, all of those must be expansions then. Oh, but wait, according to some people, they're just DLCs since they only give around 7 or 8 hours of content.
If an expansion is "a whole add on or sector", then every extra piece of content that adds to the singleplayer that isn't a weapon pack, skin pack, or armor pack (or any other cosmetic item) is a full "expansion", by way of adding more missions, quests, objectives, etc, typically in new locations with new characters. So something like Citadel for ME3 is an "expansion" in the same way that Awakening is an expansion for DAO. They both add new characters, new locations, and new enemies, along with a new storyline with more armor and weapons to obtain. Yet, for some reason, Awakening is considered an "expansion" while Citadel is just a "DLC".